(1) Field of the Invention
The present invention relates to a liquid crystal display device, and in particular, to a technology which is effective when applied to a common driver for inputting a positive or negative counter voltage in the counter electrode in each pixel.
(2) Description of the Related Art
Liquid crystal display devices using thin film transistors (TFT's) for active elements are widely used as displays for personal computers and the like. These liquid crystal display devices have a liquid crystal display panel, a drive circuit for driving the liquid crystal display panel (a drain driver, a gate driver and a common driver) and a display control circuit (timing controller).
Thin film transistors (TFT's) using an amorphous silicon layer as the semiconductor layer (hereinafter referred to as a-Si thin film transistors) and those using a polysilicon layer as the semiconductor layer (hereinafter referred to as poly-Si thin film transistors) are currently used.
The operation speed of poly-Si thin film transistors is higher than that of a-Si thin film transistors by two digits, and therefore the gate driver and the common driver (which make up the counter electrode driving circuit) are formed of poly-Si thin film transistors in liquid crystal display panels using poly-Si thin film transistors as active elements. The gate driver and the common driver are fabricated on the surface of one of the two substrates that form the liquid crystal panel, on the liquid crystal side.